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Book Chapter

Estimation of Local Anisotropy Using Polarisations and Travel Times From the Oseberg 3DVSP

By
Paul Williamson
Paul Williamson
Elf Exploration Production
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Eric Maocec
Eric Maocec
Elf Exploration Production
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Published:
January 01, 2001

Abstract

Observations of polarisations and slownesses at downhole receivers in walkaway or multioffset VSP experiments can in principle be inverted to give the anisotropic seismic velocity of the earth in the vicinity of the receiver array. In practice, such inversions have been only rarely reported, possibly due to a general lack of confidence in polarisation measurements. We apply such an inversion to the direct P-wave arrivals from a 3D VSP dataset acquired at the Oseberg field in the Norwegian North Sea. The large size of this dataset ensures that the result is more stable than those from comparable inversions applied to standard 2D datasets. Comparison with the result from the more established, but more restricted, method of inversion of surface and receiver slownesses showed a large discrepancy. Further investigation revealed that this is due to acquisition-related coherent noise on the estimated surface slownesses; there is no corresponding effect on the polarisation inversion because each shot is treated independently. We therefore prefer the result from the polarisation inversion in this case.

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Contents

Society of Exploration Geophysicists Open File

Anisotropy 2000: Fractures, Converted Waves, and Case Studies

L. Ikelle
L. Ikelle
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A. Gangi
A. Gangi
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Society of Exploration Geophysicists
Volume
6
ISBN electronic:
9781560801771
Publication date:
January 01, 2001

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